Merge 133550 - [Chromium] Unicode combining diacritical aren't always combined on Linux

Source/WebCore/platform/graphics/harfbuzz/ng/HarfBuzzShaper.cpp

 /*
  * Copyright (c) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 304 matching lines @@
 
     hb_buffer_set_unicode_funcs(harfbuzzBuffer.get(), hb_icu_get_unicode_funcs());
     if (m_run.rtl() || m_run.directionalOverride())
         hb_buffer_set_direction(harfbuzzBuffer.get(), m_run.rtl() ? HB_DIRECTION_RTL : HB_DIRECTION_LTR);
 
     for (unsigned i = 0; i < m_harfbuzzRuns.size(); ++i) {
         unsigned runIndex = m_run.rtl() ? m_harfbuzzRuns.size() - i - 1 : i;
         HarfBuzzRun* currentRun = m_harfbuzzRuns[runIndex].get();
         const SimpleFontData* currentFontData = currentRun->fontData();
 
+        // Add a space as pre-context to the buffer. This prevents showing dotted-circle
+        // for combining marks at the beginning of runs.
+        static const uint16_t preContext = ' ';
+        hb_buffer_add_utf16(harfbuzzBuffer.get(), &preContext, 1, 1, 0);
+
         if (m_font->isSmallCaps() && u_islower(m_normalizedBuffer[currentRun->startIndex()])) {
             String upperText = String(m_normalizedBuffer.get() + currentRun->startIndex(), currentRun->numCharacters());
             upperText.makeUpper();
             currentFontData = m_font->glyphDataForCharacter(upperText[0], false, SmallCapsVariant).fontData;
             hb_buffer_add_utf16(harfbuzzBuffer.get(), upperText.characters(), currentRun->numCharacters(), 0, currentRun->numCharacters());
         } else
             hb_buffer_add_utf16(harfbuzzBuffer.get(), m_normalizedBuffer.get() + currentRun->startIndex(), currentRun->numCharacters(), 0, currentRun->numCharacters());
 
         FontPlatformData* platformData = const_cast<FontPlatformData*>(&currentFontData->platformData());
         HarfBuzzNGFace* face = platformData->harfbuzzFace();
@@ skipping 190 matching lines @@
     if (!foundToX)
         toX = m_run.rtl() ? 0 : m_totalWidth;
 
     // Using floorf() and roundf() as the same as mac port.
     if (fromX < toX)
         return FloatRect(floorf(point.x() + fromX), point.y(), roundf(toX - fromX), height);
     return FloatRect(floorf(point.x() + toX), point.y(), roundf(fromX - toX), height);
 }
 
 } // namespace WebCore